In recent years the popularity of digital cameras among consumers has been making assured progress. One of the reasons that can be cited for this is that the cost of digital cameras has continued to decrease and their price has reached levels within the reach of most consumers. In order to keep the cost down most digital cameras use what is called a single-chip image pickup device. In a single-chip digital camera only one imaging elements device is used to get the color information of each of the pixels within the color image.
With single-chip imaging elements each pixel image only contains the color information of a single color. However, the color image is expressed by combining 3 separate single-color images. In other words, in order to display the color image, the red, green and blue (RGB) values of each pixel is necessary. Because of this, in single-chip digital cameras, demosaic processing (also called color interpolation processing) of each of the pixels, using the color mosaic image, having one of the RGB constituents is performed (for example, see Patent References 1 and 2). The demosaic process is a process that generates a color image with each pixel having all the RGB constituents with the use of interpolation calculation on the lacking color luminance information gathered from the surrounding pixels of the corresponding color mosaic image pixels.
Also, as an example of correction processing, chromatic aberration correction is sometimes performed. The refraction index of lenses used for the imaging optics in digital camera differs in accordance with the wavelength of the image light. Because of this, the image magnification ratio for each of the RGB colors becomes different. Due to this, the size of the image formed on the imaging elements is different for each color. It is known, as can be seen in FIG. 20, that the image formed on the imaging elements can be misaligned for each color component. This is called the lens magnification chromatic aberration (horizontal distortion). If magnification chromatic aberration is present when photographing under a white light source, the area near both edges of the frame especially look like they become more iridescent and seem to lengthen in the radial ray direction. Also, along with the image misalignment, color shifting at the edges of the frame appears and there is a problem with damage to the quality of the image.
An imaging pickup device capable of suppressing this kind of color shifting is provided such that when there is a color shifting occurrence, in accordance with the image pickup obtained color image signal, the color aberration amount from the color image base position is detected and, in accordance with the detected amount of chromatic aberration, distortion correction is added to the color image signal.
There are also image pickup devices that detect the chromatic aberration amount by detecting the effective edge within the color image and the distance from the base position.
Furthermore, there are also proposals for digital cameras that output a synthesized RGB image signal that has been corrected for chromatic aberration. This is achieved by first taking the RGB signal output from the optical lens image pickup and correcting the chromatic aberration of each (G is base and magnification or reduction correction is done for RB) with the use of the optical lens specific focal point distance value (for example, refer to Patent Reference 3).
Patent Reference 1: Tokuhyo 2004-534429
Patent Reference 2: Tokukai 2000-270294
Patent Reference 3: Tokukai Hei 6-113309